Switch contacts

ABSTRACT

A switch mechanism in which the movable contact spring and/or the fixed contact is provided with a pivotally mounted yoke forming at least one of the contact surfaces. The yoke is arcuate having a U-shaped cross section and mounted on a bearing edge formed from the contact spring so that when the spring is deflected, the yoke acts in sliding, rolling and frictional engagement with the opposing contact face.

Unite States Patent [72] Inventor Franz Jungels Frittlingen, Germany [21] Appl. No. 2,000

[22] Filed Jan. 14,1970

[45] Patented Dec. 7, 1971 [73] Assignee Heddernheimer Metallwareniabrik AG- Werk Fluorn lFluorn, Germany [32] Priority Jan. 16, 1969 [3 3 Germany [54] SWITCH CONTACTS 10 Claims, 6 Drawing Figs.

[52] U.S.Cl 200/166.], 200/67 D [51] 1nt.Cl H0111 1/34 [50] Field 01 Search 200/67 D, Y 166 BH, 166 J [56] References Cited UNITED STATES PATENTS 3,176,109 3/1965 Wodtke 200/67 D X 3,493,702 2/1970 Ramstetter 200/l66 Bl-l X Primary Examinerl-l. 0. Jones Attorneys-Richard Low and Murray Schaffer ABSTRAEIT: A switch mechanism in which the movable contact spring and/or the fixed contact is provided with a pivotally mounted yoke forming at least one of the contact surfaces. The yoke is arcuate having a U-shaped cross section and mounted on a bearing edge formed from the contact spring so that when the spring is deflected, the yoke acts in sliding, rolling and frictional engagement with the opposing contact face.

PATENTEDUEB 7197: 36261 32 SHEET 1 [1F 2 Inventor: Farm 2 Jun/e ELS PATENTED DEC 7 ISTI SHEET 2 [1F 2 mvenmr FRm/z JUMGELS b 7 OZ K WW my SWITCH CONTACTS BACKGROUND OF THE INVENTION The present invention relates to electrical switches and, in particular, to an improved contact for relay switches, pushbutton switches, microswitches and the like in which at least one movable contact member is provided.

Spring or blade contacts of many shapes and sizes are well known and interchangeably used in, not only the mentioned switches, but in various other types. In all cases, the switch briefly comprises an operating element which is effective in moving one or more contact springs or blades between two or more positions in such a manner that a connection with a fixed contact is either made or broken.

When the switch is of small dimension, such as the more recent microswitches, effective contact is difficult to obtain, resulting in arcing and the deposition of a harmful layer of oxide on the surface of the contacts. This problem is particularly prevalent when current loads of substantial magnitude are switched. An attempt has been made to overcome this problem by improving contact with the use of positive snapping operating springs. While such devices are an improvement, they do not provide an adequate rolling or frictional engagement of the contact surfaces. Rolling or frictional engagement is preferred since it allows smooth transfer of current while significantly reducing the buildup of oxide.

Another attempt at improvements provided for the simultaneous spring loading of the fixed contact which is then provided with a rigid abutment. In such dual spring switches, the fixed contact moves for a predetermined distance together with the movable contact spring until it engages the rigid abutment providing a transition period of low contact resistance and preventing a strong reduction in contact pressure prior to the snap. However, frictional and rolling engagement is not improved, the contact surfaces are not cleaned and the formation of an oxide layer still occurs, resulting in continued malfunctioning of the switch.

It is an object of the present invention to provide an improved switch mechanism.

It is another object of the present invention to provide a switch contact producing excellent rolling and frictional engagement between contact faces.

It is still another object of the present invention to provide an improved switch contact of small dimensions capable of carrying large current loads without buildup of oxide layers on the contact faces.

It is a further object of this invention to provide an improved switch construction applicable to various switch types.

These objects as well as others together with numerous advantages will be apparent from the following description.

SUMMARY OF THE INVENTION According to the present invention, a switch mechanism is provided in which the movable contact spring and/or the fixed contact is provided with a pivotally mounted yoke forming at least one of the contact surfaces.

It is preferable that the yoke be arcuate having a U-shaped cross section and mounted on a bearing edge formed from the contact spring so that when the spring is deflected, the yoke acts in sliding, rolling and frictional engagement with the opposing contact face.

Preferably, the yoke comprises a curved central back by which it is mounted to the spring contact and a pair of legs extending some distance along the length of the contact.

While it is also preferred that the yoke be mounted on the spring contact, it may also be mounted on the fixed contact or on both as desired.

These features, as well as a full and detailed description of the present invention, will be seen from the following description in which reference is made to the attached drawing.

BRIEF DESCRIPTION OF DRAWINGS In the drawings, the same reference numerals are used for the same or similar parts.

FIG. 1 is a schematic view of a double-throw microswitch having a central contact spring provided with a yoke in accordance with the present invention;

FIG. 2 is a perspective view of the contact spring and yoke of FIG. i;

FIG. 3 is a view of a device similar to that shown in FIG. ll showing a modified form of yoke;

FIG. 4 is a sectional view showing a double-throw switch having a central contact and two normally open contacts;

FIG. 5 is a view of a double-throw switch having a modified yoke; and

FIG. 6 is a schematic view illustrating the action of the contact and yoke in accordance with the present invention.

Before turning to a detailed description of the drawings, it is to be noted that the figures omit certain features conventional to switches. For example, switches normally come housed in cases, boxes or frames; they are normally provided with an operating element by which the contact spring or springs may be moved, such operating elements being manually actuated, electromechanically actuated or actuated by a prime or mechanical mover; and switches also are normally provided with mechanical detents, terminal means, holding springs, insulators, etc. These elements, as well as others, well known in this art, are omitted from the drawings for the sake of brevity and simplicity. Since the present invention is directed to the improvement of contact spring and contact face construction, only that which is necessary for its understanding is shown and described.

It is to be also understood that the following disclosure is directed to the description of contact assemblies which may be employed in any one of the variety of switches mentioned earlier. The figures and descriptions are purely schematic with regard to conventional features and many modifications and changes may be made to adapt each of the embodiments shown for a specific and particular purpose.

With the above in mind, we turn now to FIGS. 1 and 2 wherein there is shown a contact assembly of microsize comprising a movable central contact spring 1 and a pair of fixed countercontact springs 2 and 3 secured within a blocklike base 4 which may be of molded insulating material. The movable contact spring 1 is connected at its upper end 8 to one end of an arcuate spring member 6 which has its outer end connected to the free end 7 of an operating element 5 secured also within the face 4. The operating element 5 and the arcu ate spring 6 are in well-known manner so shaped and arranged to provide snap movement of the central contact spring 1 between the counterspn'ngs 2 and 3. The double-throw switch so far described is completed by furnishing each of the countersprings 2 and 3 with contact nodes Ill and 10 respectively.

The central or movable contact member 1 is provided with a yoke 9 comprising a central arcuate bearing back 9d from which extends a pair of depending legs 9b. The yoke 9, as shown in this embodiment, is generally U-shaped or horseshoe in cross section. comprising a continuous elliptical are from one edge to the other edge 9c. The yoke is elongated along an axis coincident with its back 9c, which in this embodiment is parallel to the width of the contact member and is freely positioned so that it bears on the upper edge lb of the contact spring 1. The yoke 9 is provided with a central aperture 9a, midway of its back which is adapted to fit over a projecting tab 1a extending upwardly from the edge lb in the plane of the movable contact and along its central longitudinal axis. Thus, the yoke 9 pivots about an axis (edge lb) transverse to the axis of the contact spring 1.

The pivoting motion of the yoke 9 is such that when the snap spring 6 initially forces the contact spring 1 against the fixed counterspring 2, the yoke 9 is pivoted to an extent that the edge 90 of its left leg engages the side of contact spring 1 and correspondingly, the arcuate side makes resilient engagement with face 11 of the contact spring 2, as seen in FIG. 2. When the operating element 5, however, is deflected toward the left by a suitably designed operating member, a point is ultimately reached in which the snap spring 6 instantaneously switches the movable center contact spring 1, pressing it against the opposite fixed contact spring 3. The contact yoke 9 which is mounted for pivotal movement transverse to the longitudinal axis of the contact springs simultaneously pivots until its right leg edge 90 engages contact spring 1 and its corresponding face 9b engages the contact face 10 of the counterspring 3. It is readily appreciated that during these pivotal movements of the contact yoke 9, there is additional rolling relative movement between the legs 9b, the cooperating contacts l and 11 of the fixed contacts springs 2 and 3. Preferably, the legs 9b are made convexly arcuate having a high point 20 looking towards a corresponding high point 21 on the countercontacts l0 and 11.

As is evident from the illustrated embodiment of FIGS. 1 and 2, the present invention makes it unnecessary to weld, rivet or otherwise fasten the yoke to the spring 1, and it is sufficient in most cases to merely cover the yoke 9 with a suitable contact material, its structural base being made of inexpensive material such as plastic. The projecting tab In, as seen in FIG. 2, permits the contact yoke 9 to be held in place solely by the snap spring 6. The recess 9a into which the tab la extends should be preferably big enough so that contactyoke 9 can perform the desired pivoting movement freely and without hindrance. The legs 9b are normally arranged in such a manner that their edges 9c do not touch the spring in their rest position nor do their faces touch the contacts and 11. Preferably, the frontal edges lb of the movable contact spring 1 extending laterally from the projection la are formed as knifelike edges so that the yoke 9 can pivot easily. The projecting tab la is introduced into the receiving aperture 8 at the end of the snap spring 6 in conventional manner and because of the resilient force of the snap spring 6, the yoke 9 is pressed against the knife edge lb and is thus held in its uniquely defined position.

The embodiment shown in FIG. 3 illustrates the situation where the fixed countercontact springs 2 and 3 rather than the central spring I carry contact yokes. The movable contact spring 1 is provided with conventional contact heads or rivets 30 or may just be covered with a layer of contact material. The snap mechanism of the springs 6 and 5 corresponds to that of the switching contacts shown in FIG.. 1. In this form, the yokes 12 and 13 are mounted directly on the upper edge of each counterspring 2 and 3 respectively. The countersprings 2 and 3 are, of course, not furnished with the usual contact faces, but each spring is furnished with a bearing edge 14 and 15 respectively which may be the same as described in connection with FIG. 1, ie having a knifelike bearing edge lb and projecting tab la. On the other hand, it may be modified, as for example, to provide a U-shaped edge with upward projections at each end in which the yokes 12 and 13 sit. The leg of the yokes l2 and 13, however, are extended and are secured in the base block 4 to become part of the spring action of the countersprings 2 and 3.

When the movable contact spring 1, as shown in FIG. 3, is pressed toward the inner face of the left yoke 12, the yoke 12 pivots on the bearing 14 until he free leg engages the fixed contact spring 2. The fixed leg of the yoke 12 is correspondingly deflected and produces a corresponding resilient counterforce together with the counter 2. It will also be observed that when yoke 12 is pivoted on the bearing edge 14, the desired rolling and frictional movement between the face of the yoke 12 and the contact point of the movable contact spring 1 is also produced.

In FIG. 4, the embodiment is similar to that shown in FIG. 1 and the movable contact spring 1 and the fixed countercontact springs 2 and 3 are also secured in a base block 4 so that the movable contact spring 1 and the contact yoke 9 are located midway between and normally not in contact with the countersprings 2 and 3. The yoke 9 is loose and freely pivotally supported by its back on the bearing edge 16 of the spring I, which has its tab 160 extending vertically upward into a horizontal operating element 18. The yoke 9 is dimensioned so that the free ends 9c of its legs do not engage fixed contacts 10 and 11 in the rest position between the countercontacts 2 and 3.

The tab 16a of movable contact spring 1 is positioned in a hole or aperture 17 of the operating element 18 and can be deflected in both directions so that in one case a connection is established between the movable contact spring 1 and the fixed counterspring 2, and in the other case connection is made between the movable contact spring 1 and the fixed contact spring 3. In each switching position, the contact yoke 9 assumes the same pivotal action and terminal movement so that an adequate rolling frictional movement is achieved between it and the contact faces 10 and 11 as described in connection with the previous embodiments. If desired, the spring 1 can be held by means of an additional resilient operating element in a desired starting position against one of the countersprings 2 and 3. However, the arrangement shown in FIG. 3 has the advantage that the distance of the two fixed countersprings and 3 can be reduced and the flexing of the spring 1 minimized.

It may sometimes be of advantage to arrange the axis of the yoke 9 parallel to the longitudinal axis of the contact spring. FIG. 5 shows a microswitch similar to that of FIG. 1 whose movable contact spring 1 carries a projection lb on one of its narrow vertical sides, the portions adjacent to which being formed with a knife edge bearing as previously described. The back 9d extends parallel to the axis of the spring I so that the legs 9b extends transversely thereto. Advantageously, when the switching elements 5 and 6 are operated, the yoke 9 performs a continued pivotal movement which enhances the relative frictional and rolling movement between the yoke 9 and the contacts 10 and 11. This movement is directed both parallel to and transversely of the longitudinal axis of the legs of the yoke 9 because of the combined pivoting of the yoke and the circular arcuate movement of the springs.

The manner in which the frictional and rolling movement between the yoke and the spring occurs will now be explained with reference to FIG. 6 which shows a portion of the device shown in FIG. 1. Let it be assumed that the movable contact spring 1 is in normal initial condition pressed against the nonillustrated fixed contact spring 3. The left leg of the yoke 9 therefore is rather remote from the contact spring I with its highest point 20 directed toward but spaced from the highest point 21 on the contact 11 of the fixed counterspring 2. When the operating spring elements (5 and 6) are actuated, the snap spring 6 instantaneously causes the spring 1 to move in a circular are 19 generating a small component of movement in the direction of the longitudinal axis of the contact spring 1 which is simultaneously enlarged by the pivoting movement of the contact yoke 9 as it strikes the face 11. When the contact spring 1 snaps, the highest point 20 of the left leg of the yoke 9 abuts and engages the highest point 21 of the face 11 of the counterspring 2. As the spring 1 moves into its final rest position, the yoke 9 pivots so that its point of contact 20 moves downwardly, as seen in dotted lines, so that the high point 20' slides beneath the high point 21 of the face 11. Thus, from one position to another, the contact yoke 9 frictionally rolls from one point of contact to another along the face 11 and the added frictional movement for cleaning the contact is achieved even if the contacts are of minimum dimensions and of the simplest construction.

The invention may take various forms, as for example, if the yoke is mounted on the front side of the movable contact spring, the path of frictional engagement between the leg of the contact yoke and the fixed contact is increased because the free end of the movable contact spring itself moves in a circular path and furnishes a component of rotary movement. As seen, the yoke itself may be mounted in two possible ways, in one of which the yoke is arranged with its back transverse to the longitudinal axis of the movable or fixed contact springs and legs extend in the direction of their longitudinal axis; while in the second way, the yoke is arranged with its back in the direction of the longitudinal axis of the spring contact so that the legs of the yoke extend transversely to the longitudinal axis of the spring contact. In either case, the pivotal or rocking movement of the yoke insures frictional movement during opening and closing of the switch contacts from one position to another.

The invention is applicable to normally open, normally closed or double-throw switches. as well as multiple contact switches having a common operating element or separate operating element. The switching contact may be controlled by an electromagnetically or mechanically operating element as in conventional relays.

When the yoke is associated with a fixed countercontact, a unique starting position can be achieved according to the invention by extending the yokes on the fixed countersprings on the side facing away from the movable contact springs and affixing it in base block as shown in FIG. 3.

By making the yoke continuously arcuate, the rolling movement between its legs and the cooperating countercontact face is enhanced. The yoke thereby is assured of continuous rolling on the cooperating countercontact.

The switching behavior of the new switch contacts with respect to sudden jolts is improved by the fact that the yoke itself may be made of springlike material. The yoke can be produced from cheap electrically conductive material, or in specific cases, of a base of plastic material covered only on the side directed toward the cooperating contacts with conductive material.

Particularly good switching behavior is achieved with the simple arcuate snap spring shown in FIGS. ll, 3 and 5 even when the device is used in small microswitches. This snap spring is also advantageously employed to position the contact yoke and to hold the yoke resiliently superimposed on the bearing edge of the movable contact spring. The arrangement being preferred is where the movable contact spring carries a projecting tab which enters into a recess in the yoke back, serving both to guide the latter and engage an aperture in the snap spring in hooklike manner. A further advantage is obtained by providing the bearing edge movable contact spring in the shape of a knife edge forming an elongated fulcrum for the back of the yoke.

The invention is also applicable to switches in which the superimposed yokes do not have a unique initial or starting position, but are normally arranged so as to be located spaced from the opposed contacts as seen in FIG. 4.

Numerous modifications have been suggested, and it will be obvious to those skilled in the art that many more changes and modifications are available without departing from the scope of the invention disclosed herein. The present disclosure is to be taken, therefore, as illustrative only.

What is claimed is:

it. An electrical switch comprising a movable contact member, at least one opposed countercontact member, means for moving said movable contact member into engagement with a selected one of said countercontacts, and a yoke carried by at least one of said contact members said yoke providing a contact surface between said carrying contact and said opposed contacts, said yoke having a portion forming a first bearing surface, said carrying contact having a portion forming a second bearing surface, said bearing surfaces cooperating to support said yoke on said carrying contact for pivotal movement with respect thereto, whereby said yoke effects sliding engagement with the opposing contact.

2. The switch according to claim 1,. in which the yoke comprises a U-shaped member having a central back portion forming the first bearing surface, and a pair of extending leg portions convexly arched about an edge of said carrying contact towards the opposed contacts.

3. The switch according to claim 2, wherein the yoke is resilient.

4. The switch according to claim 3., wherein the yoke comprises a body coated with conductive material.

5. The switch according to claim 2, wherein the back of said yoke is arranged in a direction transverse to the longitudinal axis of the contact and the legs extend in a direction parallel to the longitudinal axis.

6. The switch according to claim 2, wherein the back of said yoke is arranged in a direction parallel to the longitudinal axis of the contact and the legs of the yoke extend in a direction transverse to the longitudinal axis.

7. The switch according to claim 2, wherem said yoke IS mounted on the countercontacts and have one leg extending longitudinally along the face thereof and secured at the end against movement.

8. The switch according to claim 1 including a snap spring activating said movable contact, said snap spring being adapted to engage and hold said yoke on said contact.

9. The switch according to claim ll wherein the contact has a projecting tab extending into a recess formed in said yoke to hold the same.

10. The switch according to claim ll wherein said yoke is mounted on said movable contact, said movable contact being located between two countercontacts and spaced uniformly from each. 

1. An electrical switch comprising a movable contact member, at least one opposed countercontact member, means for moving said movable contact member into engagement with a selected one of said countercontacts, and a yoke carried by at least one of said contact members said yoke providing a contact surface between said carrying contact and said opposed contacts, said yoke having a portion forming a first bearing surface, said carrying contact having a portion forming a second bearing surface, said bearing surfaces cooperating to support said yoke on said carrying contact for pivotal movement with respect thereto, whereby said yoke effects sliding engagement with the opposing contact.
 2. The switch according to claim 1, in which the yoke comprises a U-shaped member having a central back portion forming the first bearing surface, and a pair of extending leg portions convexly arched about an edge of said carrying contact towards the opposed contacts.
 3. The switch according to claim 2, wherein the yoke is resilient.
 4. The switch according to claim 3, wherein the yoke comprises a body coated with conductive material.
 5. The switch according to claim 2, wherein the back of said yoke is arranged in a direction transverse to the longitudinal axis of the contact and the legs extend in a direction parallel to the longitudinal axis.
 6. The switch according to claim 2, wherein the back of said yoke is arranged in a direction parallel to the longitudinal axis of the contact and the legs of the yoke extend in a direction transverse to the longitudinal axis.
 7. The switch according to claim 2, wherein said yoke is mounted on the countercontacts and have one leg extending longitudinally along the face thereof and secured at the end against movement.
 8. The switch according to claim 1 including a snap spring activating said movable contact, said snap spring being adapted to engage and hold said yoke on said contact.
 9. The switch according to claim 1 wherein the contact has a projecting tab extending into a recess formed in said yoke to hold the same.
 10. The switch according to claim 1 wherein said yoke is mounted on said movable contact, said movable contact being located between two countercontacts and spaced uniformly from each. 